The present invention relates to a track vehicle construction in which a wheel is carried by a hub and motor assembly which is supported by a mount assembly that is adjustable, for varying track tension as required.
Vehicles have been provided with tracks which extend around at least two wheels or sprockets which are carried by the chassis of the vehicle, usually on suitable bearings. After a period of use, it has been recognized that the track tends to lengthen, and thereby in order to maintain proper tension of the track, various constructions have been utilized for enabling the track to be tensioned, so that there is less danger of the track separating or coming off of the wheels. In a number of instances, one of the wheels has been mounted on a bearing which is movably mounted on the chassis of the vehicle, there being provided a hydraulic shift motor which is utilized to shift the movable wheel away from the other wheel, so as to in effect lengthen the distance between the axles and thereby increase track tension as necessary. In addition, there have been provided constructions in which the adjustment secured is maintained either by the hydraulic cylinder, or by a separate mechanical arrangement. In the latter constructions, the hydraulic shift cylinder is used only for obtaining the desired position of the wheel and the consequent track tension adjustment, and the position of the wheel is then maintained by a mechanical lock.
In one known construction, for example, a separate track frame was provided, supported from the main chassis of the vehicle, and this separate track frame included longitudinally extending upper and lower guides. The bearing of the non-driven wheel was supported in these guides, and the axle of the non-driven wheel was carried in the bearing. A thrust rod was provided, having one end engaging the bearing and the other end serving as a piston in a hydraulic shift motor, the cylinder of the hydraulic shift motor being bifurcated, and clamp means were provided to selectively clamp the bifurcated ends of the hydraulic shift cylinder to the piston portion of the thrust rod, to thereby secure the desired adjustment position of the wheel bearing and axle. This construction, therefore, required a separate track frame, and therefore was both heavy and expensive and not suitable for lighter weight tracked vehicles.
A similar construction including a separate track frame was provided in another known apparatus, the distinction being in the specific mechanical locking arrangement, in this construction there being provided teeth on the piston of the shift motor, with the shift motor cylinder having an opening in which was inserted a toothed locking plate which could be secured in the locked position by nuts and bolts forcing it inwardly against the toothed piston rod, or, selectively, permitting the toothed locking plate to be disengaged from the piston rod to permit movement of it. This construction was deficient for the same reasons as the construction above discussed, and additionally permitted only set-by-step adjustment, and not unlimited adjustment.
In yet another disclosure of the prior art, a somewhat different locking arrangement was provided being characterized by a piston rod having grooves transverse to the longitudinal axis of it, there being provided a horseshoe-shaped locking member which could be inserted into one or another of the grooves, and which could engage the end of the cylinder of the the shift motor, so as to lock the shift motor in the desired position.
These noted constructions, while providing suitable strength, usually by the utilization, of an additional track frame, were deficient in requiring a heavy construction, with an auxiliary track frame, and also in not providing for a construction in which the wheel subject to adjustment would be a driving wheel.